Load-controlling apparatus for compressors



April 3, 1945. YERGER 2,372,923

LOAD-CONTROLLING APPARATUS FOR, COMPRESSORS I Filed July 7, 1942 6Sheets-Sheet l INVE NTO F? Paul fileryer.

H I 5 ATTORN EY.

April 3, 1945. R YERGER 2,372,923

. LOAD-CONTROLLING APPARATUS FOR COMPRESSORS I Filed July '7, 19426.5heets-Sheet 2 NvENTo Paafl 3 2 en BY 4% M2;

HIS ATTORNEY,

April 3, 1945. P. A. YERGER 2,372,923

LOAD-CONTROLLING APPARATUS FOR COMPRESSORS Filed July 7, 1942 6Sheets-Sheet 3 April 3, 1945. P. A. YERGER LOAD-CONTROLLING APPARATUSFOR COMPRESSORS Filed July 7, 1942 6 Sheets-Sheet 4 5 mF H A 6 W 2 8 a 1a 1 I 2 1 0 m awn lllll 1|.- L

|N\ /ENTO R Bull H1 8 BY ryez'.

H \5 ATTORNEY.

April 3, 1945. i YERGER 2,372,923

LOAD-CONTROLLING APPARATUS FOR COMPRESSORS Filed July '7, 1942 6Sheets-Sheet 5 II .19 25a :57

INVENTOR I)BY.PaulZI'Y:- ev- Hl$ ATTORNEY.

April 1945. P. A. YERGER LOAD-CONTRQLLING APPARATUS FOR COMPRESSORS 6Sheets-Sheet 6 Filed July 7, 1942 INVENTOR.

lauilI-YE BY I HIS ATTORNEY- ly, above and below the point ofcommunication of the conduit BI with the valve chamber and thus, ineffect, define a movable chamber 64 for pressure fluid to supply themain valve chambers. Such pressure fluid is conveyed from the supplychamber 64 to the valve chambers 48, 49, 59 and;

|, for distribution by the main valves, through passages 65, 66, 61 and68, respectively, in the casing 41, said passages lying in the sametransverse plane as the conduit 6| so that the main valve chambers willat all times be in communication with pressure fluid supply. I

In order to effect actuation of the main valve the casing 41 is providedwith two groups of kicker passages that are controlled by the pilotvalve 56. One group of kicker passages opens into the valve chamber 51at points intermediate the supply conduit GI and the exhaust port 58 andthe other group opens into the valve chamber at points intermediate thesupply conduit and the exhaust chamber 59. By reason of this arrangementthe passages constituting the lowermost group may be communicated witheither the atmosphere or with pressure fluid supplyby the flange-63 ofthe valve, and thepassages constituting the uppermost group may becommunicated with the source of pressure fluid supply or with theexhaust chamber 59 by the valve flange 52, accordingly as the valve 56is raised or lowered in the valve chamber 51. More specifically, akicker passage 69-leads from the lower part of the valve chamber 51 tothe corresponding end of the valve chamber 48, and other passages 19, Hand 12 of the same group and communicating with the valve chamber 51 atprogressively higher elevations lead to the lowermost ends of the valvechambers 49, 50. and 5|, respectively. 'In this connection it might bestated that the points of communication of the passages 69 to 12-withthe valve chamber 51 are spaced equi-distantly with respect to eachother and a greaterdistance apart than the width of the flange 63controlling them.

The pressure fluid serving to move the main valves totheir lowermostlimiting positions is con veyed into the valve chambers 48, 49, 59 andSI by kicker passages 13, 14, 15 and 16, respectively. The point ofcommunication of these passages with the valve chamber 51 is controlledbythe flange 62 of the valve. They lie at progressively increasingelevations, in the order named, and like the lowermost group of passagesare so spaced with respect to each other that the flange 92 may coveronly one passage in any position that the pilot valve may assume.

As in the aforesaid patent, each main valve has upper and lower heads 11and 18, respectively, that are connected by an axial stem 19. Each stem19 carries a block 89 the outer surface of which slidably engages thewall of the valve chamber and has a recess 9| to afford communicationbetween the supply conduits for the clearance valves and exhaustpassages 82, in the casing 41, leading to the exhaust chamber 59. Themain valves may be held in any suitable manner against rotation, andbetween the lower ends of the blocks 89 and the heads 18 are spaces 83through which pressure fluid flows from the main valve chambers to theconduits 42, 43, 44 and 45 in the uppermost positions of the mainvalves.

The movement of the pilot valve 56 endwise of the valve chamber 51 iseffected, in part, by a main actuator comprising a weighted lever 84,one end of which hinges on a pivot 85 seated in a frame 86 that may besuitably supported by the compressor 29. The lever 84 rests upon a pin81 at a point between the pivot 85 and a weight 88 that isslidablyadjustable upon the beneath the diaphragm 99. -The chamber 92 is inconstant communication with the storage receiver 24 through a conduit 93to subject the diaphragm constantly to the pressure existing in thestorage receiver.

In accordance with the practice of the invention, means are provided tocause the load-com trolling apparatus of the compressor to effect itsload-varying function in response to only slight variations in the valueof the pressure of the fluid in the receiver system of the compressorand to assur a positive action of such apparatus. To these ends themovement of the lever 84 is imparted to the pilot valve 56 bytransmission mechanism designated in its entirety by 94. Thetransmissionmechanism may be arranged in a suitable casing 95, asillustrated more particularly in Figure '7 of the drawings, andcomprises a hollow shaft 96 having an external flange 91 at one end thatcarries a lever 98. The free end of said lever is pivotally connected toan end of a.

link 99 having its other end pivotally connected to the end of the lever84. Owing to this arrangement the oscillatory movement of the lever 84,about its pivot 85, will be transmitted to the hollow shaft 96 to causesaid shaft to describe a similar movement.

The flange 91 forms a cover for and is rotatable with respect to a gearcasing I99 having a recess IM to accommodate differential gearingincluding an internal gear I92 that meshes with a pinion I93 rotatableon a shaft I94 seated in the outer end surface of the flange 91. Thepinion I93 also meshes with a gear I95 keyed to a shaft I96 that extendsaxially through the hollow shaft 96 and has portions on the oppositesides of the gear I95 journaled in the flange 91 and in the gear casingI99.

The shaft I96 is additionally supported by a bearing I91 in the outerend of the hollow shaft 96, and on the shaft I96 adjacent the bearingI91, is-a gear I98 that is locked to the shaft I96 by a set screw I99.The latter gear meshes with a rack II9 carried by the pilot valve 56 sothat when the shaft I96 is rotated the pilot valve will be moved endwiseof the valve chamber 51, either up or down depending upon th directionof rotation of the shaft I96. The arrangement of the shafts and thegearing employed for transmitting movement from one shaft to the otheris such that the pilot valve 56 will at all times follow the movement ofthe weighted lever 84.

Within the casing 95 is a frame, designated in its entirety by III,which is secured at one end to the casing 95 by bolts H2 and forms asupport for thetransmission mechanism 94. The frame III comprises ahousing II3 to receive the rack II9 and the gear I98 and has a hollowextension II4 the outer end of which constitutes a bearing H for anintermediate portion of the hollow shaft 96 to hold said shaft coaxialwith the bearing H5, and on the opposite side of the housing -I I3 is ahearing I I6 for the shaft I06.

The housing I I3 is held in the assembled position by bolts II Ithreadedly connectedto the housing and extending through the flange II8of a distance piece I I9 which itself is secured to the casing 95 by thebolts I I2. Spacers I encircling the bolts I I1 abut the housing I I3and the flange II8 to hold the housing in suitably spaced relation withrespect to the distance piece,

As will appear obvious from the foregoing description the pilot valve 56is actuated in a positive manner, in response to movement, howeverslight, of the lever 84. In order, thereforato preclude a hunting actionof the pilot valve and consequently a wavering action of the clearancevalves, means are provided for imparting movement to the pilot valveindependently of the main actuator for shifting the pilot valve from onecontrolling position to another. To this end the gear casing I00 isrendered rotatable relatively to the shafts 90 and I06. The gear casinghas a shaft portion I2I arranged coaxially with the shaft I06 andjournaled at its free end in a bearing I22 in the distance piece H9. Theshaft [2! is additionally supported by a bearing I23 that lies betweenthe gear casing I00 and the distance piece and forms an integral part ofa plate I24 that is secured to the end of the distance piece by screwsI25.

In the opposed surfaces of the distance piece and the plate I24 is arecess I26 to accommodate a gear I21 that is secured to the shaft I-2Iby a set screw I28 and meshes with a rack I29 extending slidably intothe recess I for eflecting rotary movement of the gear casing I00. Atone end of the rack is a flange I30 that may be secured, in any wellknown manner, to an end of an actuating element I3I having its other endsuitably aifixed to a bracket I32 which may be secured to a support bybolts I33.

In the form shown, the actuating element I3I is extensible andcontractible endwise in the plane of movement of the rack I29, beingactuated in one direction by pressure fluid and in the oppositedirection by spring pressure. In a more specific sense, it consists of aseries of pairs, four in the present instance, of bellows designated bypairs as I34, I35, I30 and I3! and, as will be readily apparent, equalin number of pairs the control positions of the pilot valve and thepairs of clearance valves. Each pair of bellows includes. a primarybellows I38 and a secondary bellows I39, and between theends of adjacentbellows are heads I40 that may be secured to the. bellows in anysuitable manner, as for example by welding.

A suitable head MI is also provided for the secondary bellows I39 of theend pair designated I31, and in each head is a passage I42 for theadmission and exhaust of pressure fluid into and from the bellows. Aplate I43 is interposed between the flange I30 and the adjacent bellowsI30, and in the marginal portions of each head I40 and in the bracketI32 are apertures I44 to accommodate bolts I45 that serve, in part, tomaintain all portions of the actuatin element substantially the sameaxial plane.

The bolts I45 extend loosely through the apertures I44 and spacers I 46in therorm of sleeves are disposed about them' to engage-the marginalportions of the heads I40 for limiting the extent of contractilemovement ofthe bellows. Each 'bolt carries a nut I4-I on one end thatseats against the end surface of a head positioned at one end of abellows, and a nut I48 is threaded on the other end of each bolt to actas a support for a plate I49 serving as a seat for a spring I50encircling the bolt and acting against a head at the other end of thesame bellows for effecting contractile movement of the bellows.

The nut I48 is adjustable on the bolt so that the tension of the springI50 may be varied, if desired, and on the portion of the bolt encircledby the spring I50 is a collar I-5I to engage the adjacent head I40 forlimiting the degree of extension of the bellows. Thus, the distancebetween the oppcsed surfaces of the collars I 5| and the nuts I4!determine the length that each bellows may be extended and the nuts I 41are, of course, adjustable on the bolts I45 so that such distance, aswell as the total length of extension of the actuating element I3I, maybe varied.

The flow of pressure fluid to and from the bellows is initiatedsimutlaneously for both bellows of a pair and simultaneously with thedelivery to and the exhaust of fluid from the clearance valves. Aconduit I52 is accordingly extended from the conduit 42, of theclearance valves 2'I--29, to the -port'I42 of the primary bellows of thegroup designated I34, and a branch conduit I53 leads from the conduit I52 to the secondary bellows I39 of said pair. In like manner a conduitI54 and its branch conduit I55 lead, respectively, to the primary andsecondary bellows of the pair designated I35 and communicate with theconduit 43 leading to the clearance valves 3 I--33.

Similar conduit arrangements are provided for the remaining pairs ofbellows, that is to say, a conduit I56 and a branch I5! leadingtherefrom are connected to the primary and secondary bellows of thegroup designated I35 and to the supply conduit 44 of the clearancevalves 3530, and a supply conduit I58 and a branch I59 are connected,respectively, to the primary and secondary bellows of the pairdesignated I37 and communicate with the conduit 45 leading to theclearance valves 38-40.

In the form of the invention illustrated, the admission and exhaust ofpressure fluid take place unrestrictedly only in the primary bellows I38of each pair and at the same rate as the fluid flow to and from theclearance valves. The flow of pressure fluid to and from the secondarybellows I39 of the several pairs, on the other hand, is restricted sothat a greater time interval is required for the full extension and theeffective contraction of said secondary bellows than for the primarybellows.

The mean controlling such delayed action of the secondary bellows mayconsist, as shown, of valve mechanism #50 interposed in the branchconduits I53, I55, I51 and I59. The valve mechanism I60 comprises acasing IIiI having passages I82, I53, I04 and I05 that aifordcommunication between the sections of the branch conduits I53, I55, I51and I59, respectively. Each passage in the valve casing I'EI has arestricted portion I60 that is controlled by a needle valve I5? threadedinto the casing. Suitable packing material I58 is disposed in the casingIt! to encircle the stem portion of the needle valve and said packing.

material may be compressed by a gland it?) which also serves as a guidefor the needle valve.

As a preferred arrangement, means are provided to enable all the needlevalves to be adjusted simultaneously and in the same degree with respectto the restricted portions I56 so that the effective flow areas theydefine will be the same in each of the passages in the valve casin I-BI.The needle valve are accordingly provided with cranks I that arepivotally connected to a beam I 1| whereby all the needle valves may besimultaneously rotated toward or away from the mouths of the restrictedportions I65.

Convenient means for effecting such adjustment of the needle valves andfor holding them of the aperture I are concavities I15 to receive aconvex end surface I11 on the head of the screw I12 and a similarsurface I11 on a nut I18 threaded on the screw I12 for locking saidscrew 7 fixedly in position.

In the operation of the compressor and assuming that the pressure in thereceiver system is between the minimum and maximum values at which theload-controlling devices become operative the pilot Valve 55 will assumea position to communicate all of the passages leading to the lower endsof the main valve chambers of the regulator 46 with pressure fluidsupply. The pressure fluid thereby admitted into the main valve chamberswill hold the main valve in their uppermost limiting positions. Pressurefluidwill then flow from the main valve chambers through the spaces 83in the main valves and the conduits 43, 42, 44 and 45 to the clearancevalves and maintain all of the clearance valves in closed position toprevent communication between the compressor cylinders and the clearancchambers.

At the same time, pressure fluid flowing through the conduits I52 to I58inclusive, and their branches will inflate the bellows and cause fullextension of the actuating element I3I to the limit permitted by thenuts I41 and the shoulders I5I. The actuating element I3I will remainfully extended as long as the pilot valve occupies substantially theposition described and variations in the value of the pressure withinthe storage receiver will not have the effect of causing movement ofagainst the diaphragm 90 and any movement imparted thereby to the lever84 will be transmitted by the hollow shaft 95, the pinion I03, the gearsI05 and I00 and the shaft I06 to the pilot valve 56. Thus, if in thesepositions of the parts the discharge output of the compressor exceedsthe demand the increasing pressure in the storage receiver will causethe lever 84 and the pilot valve to rise and when the predeterminedmaximum pressure is attained in the storage receiver the pilot valvewill have reached a position to partly uncover the passages 69 and 13.The pressure fluid in the lower end of th main valve chamber 48 willthen be exhausted to the atmo-sphere and pressure fluid willsimultaneously be admitted into the upper end of said valve chamberandmove the main valve 52 to its lowermost limiting position.

In the new position of the valve 52 the conduit 42 will be incommunication with the atmosphere through the recess 8 I, the passage82, the exhaust chamber 59 and the ports 50 to permit the immediateexhaust of pressure fluid from the clearance valves 21-29 and also fromthe primary bellows I38 of the pair I34. Upon the exhaust of fluid fromthe said primary bellows the associated spring I50 will contract saidbellows and cause the rack I29 to rotate the gear casing I00 in aclockwise direction, as Figure 7 is viewed from the right hand side ofthe drawings.

These movements of the gear casing and of the internal gear I02 willrotate the pinion I03 in the same direction and will have th efiect ofturning the shaft I06 and the gear I08 in a counterclockwise directionand move the pilot valve upwardly to a position in which the flange 63is approximately midway between the passages 69 and Ill. The flange 82will then also occupy a similar position with respect to the passages 13and 14. In this way the pilot valve is shifted immediately out of acontrolling position into a neutral position and at the pressureexisting in the storage receiver at the instant the pilot valve is movedthrough the controlling posit.on. The flanges of the pilot valve arethen well removed from the adjacent passages leading to the main valvechambers and the pressure conditions in these passages and associatedchannels will, therefore, not be disturbed by a possible wavering actionof the pilot valve incident to the part.al unloading of the compressor.

At the instant the conduit 32 is communicated with the atmosphere fluidwill also exhaust from the secondary bellows I30 of the pair I34 butthis flow takes place comparatively slowly and, assuming that the needlevalve I61 occupies a correct position of adjustment, at such a rate thatthe contractile movement of the secondary bellows, transmitted throughthe transmission mechanism 94 and off-set to some extent by the downwardmovement of the arm 84, will carry the pilot valve to a position inwhich only sufficient portions of the passages 10 and 14 remainuncovered to assure the retention of the main valve 53 in its uppermostlimiting position. The pilot valve will then occupy a position in whichonly a slight increase in the pressure in the storage receiver actingagainst the diaphragm will carry the pilot valve through this newcontrollin position.

In actual practice, it has been found that only a matter of a fractionof a pound increment in receiver pressure is required to thus elevatethe pilot valve to a position for cutting off communication between thepassage 10 and pressure fluid supply and between the passage 14 and theatmosphere and at the same time to place the passage 10 in communicationwith the atmosphere and the passage 14 in communication with pressurefluid supply.

After the pilot valve has been thus again shifted the same sequence ofevents following the shifting upwardly of the valve 52 will take placewith respect to the valve 53 and the elements controlled thereby, thatis to say, the pressure fluid will be exhausted from the clearancevalves 3I33 and successively from the bellows comprising the pair I35 sothat the compressor will then be operating at one-half load. The pilotvalve 56- will then again be so positioned, by

the action of the bellows of the pair I35, that only a slight additionalincrease of receiver pressure will be required to move the pilot valveupwardly for initiating another step of unloading.

The remaining groups of load-controlling and completely unloaded. This,however, is true only in the event that pressure fluid consumption isless than delivery to the storage receiver, so that the receiverpressure continues to increase, and is not a necessary incident to theoperation of the compressor and its load-controlling apparatus.Obviously, under all fractional load conditions at which the compressormay operate the demands upon the storage pressure may be in excess ofimmediate delivery to the storage receiver to cause a decreasingpressure therein. In such event additional load will, of course, beapplied to the compressor by the load-controlling devices which willthen operate in an order that is a reversal of the sequence of theiraction for efiecting the unloading of the compressor. Thus, if thecompressor is operating at, say, one-half load and in which case thepilot valve is positioned so that its flange 63 partly overlies thepassage H and the flange 62 trated, Figures 9 to 13 inclusive, thecompressor a. position to which the pilot valve had been moved inanticipation of a continued increase of receiver pressure, the pilotvalve will, by reason of the falling receiver pressure, at once movedownwardly in the valve chamber 51. In so doing the said valve uncoversthe upper portions of the passages 14 and 18, thereby releasing thepressure fluid in the upper end of the main valve chamber 49 to theatmosphere and simultaneously valving pressure fluid from the chamber 54into the lower end of said main valve chamber.

The main valve 53 will then be shifted upwardly and admit pressure fluidthrough the conduit 43 to the clearance valves 3I--33, to close in whichthe flange 63 lies midway between the 7 passages 18 and 69 and theflange 62 will occupy a similar position with respect to the passages 13and 14.

In the new position the pilot valve will then be prevented from movingto a point in the valve chamber 51 at which a variation in the pressurein the receiver resulting from the appl cation of additional load to thecompressor, and causing movement of the main actuator. might shift thesaid valve into such position with respect to the passages lyingdirectly on opposite sides of the valve flanges that the ma n valve 53and, therefore, the elements which it controls would be caused to actprematurely. The pilot valve may, however, be shifted slightly by themain actuator acting in response to a pressure rise in the receiversystem following the reloading of the compressor. Such movement will,however, be ofi-set by the delayed action of the secondary bellows I39of the pair I which, acting through the transmission mechanism 94, willmove the pilot valve to the lowermost permissible position in which thepassage 69 leading to the main valve chamber 48 may still remain incommunication with the atmosphere and a sufiicient area of the passage13 will remain in communication with the chamber 64 to assure theretention of the main valve 52 in its lowermost limiting position.

These flow areas of the passages 89 and 13 need be of only small degreeso thatxmly a slight is provided with both pneumatically andelectrically actuated devices for controlling its load. Included amongthese devices are a series, in the present instance four, valvemechanisms designated I19, I88, IBI and I82 and shown in detail inFigure 13. The said valve mechanisms are each actuated by a solenoid I83and control the flow of pressure fluid to the clearance valves of thecompressor 28 and also to the actuating element IN. The valve mechanismsare, moreover, each connected to a common pressure fluid supply conduitI84 leading from the storage re-v ceiver 24 and also to a common exhaustconduit I85 that provides an outlet for the fluid exhausted from theclearance valves and from the actuating element. g

The valve mechanisms I19 to I82 are of identical construction andcomprise a casing I86 that is recessed to provide a chamber I81 throughwhich pressure fluid flows to and from the actuating element I 3| andthe clearance valves. In the form of valve mechanism shown the GasingI86 is provided on opposite sides of the chamber I81 with recesses I88and I89 that are respectively in constant communication with the s'up-'ply conduit I84 and the discharge conduit I 85.

Communication between the recess I88 and the chamber I81 is efiectedthrough a passage I 98, in a bushing I9I threaded into the wall of thecasing I86, and is controlled by a poppet valve I92, the stem I93 ofwhich extends into the chamber I81. The valve I 92 is normally heldagainst its seat by a spring, I94 interposed between the valve I92 and aplug I95 forming a closure for the outer end of the recess I88.

In like manner, a bushing I96 is arranged between the recess I 89 andthe chamber I81 and has a. passage I91 to aiiord communication betweensaid recess and the chamber. The passage I91 is controlled by a valveI98, also of the poppet type, having a stem I99 that extends into thechamber I81. The valve I98 is urged against its seat by a spring I94interposed between the said valve and a plug I95 threaded into thecasing I86 to seal the recess I89.

The valves I92 and I98 are both unseated by a common element shown asbeing in the form of a bar 288 that is pivoted at its outer end on a pin28I which may be seated in the casing I88. The bar lies between the freeends of the valve stems I93 and I99 so that when said bar is oscillatedin the chamber IB'I one or the other of the valves will be unseated.

The inner end of th bar 288 is in the form of a sphere 282 and is seatedin an end of an armature 283 extending into the chamber I81. Thearmature 283 is slidable, in a well known manner, within the core 284 ofthe solenoid I83 and said solenoid may be suitably afflxed to the casingI36 I I80 to the clearance valves 3I33, a conduit 208 affordscommunication between the clearance valves 35-36, and the valvemechanism I8I and the remaining pair of clearance valves 38-40 areconnected with the valve mechanism I82 by a conduit 209.

As a preferred arrangement the conduits supplying pressure fluid to theactuating element I3I are connected to the conduits leading from thecontrol valve mechanisms to the clearance valves. Accordingly, theconduit 2I0 leads from the conduit 206 to th primary bellows I39 of thepair designated I34 and has a branch 2II extending to the secondarybellows I39 of the said pair.

Similarly, a conduit 2I2 extends from the conduit 201 to the primarybellows I38 of the pair designated I35 and a branch 2I3 leads from theconduit 2I2 to the secondary bellows of the last mentioned pair ofbellows. In like manner the primary bellows I38 of the pair designatedI36 is in communication with the conduit 208 through a conduit 2! 4 anda branch 2I5 leads from the latter conduit to the secondary bellows I39of the last mentioned pa r of bellows, and the primary member I38 of theremainin pair I31 .of bellows is connected to the conduit 209, by aconduit 2I6 having a branch 2!! leading to the secondary bellows I38 ofsaid pair.

In this form of the invention the flow of pressure fluid to and from theprimary bellows of each pair also takes lace unrestrictedlv and'valvemechanism I60 s m lar to that described in connection with the form ofthe invention shown in Figure 1 is interposed in thebranch condu ts 2IIto 2II inclusive in order to restrict the flow of pressure fluid to andfrom th secondary bellows to delay their actions.

The energizat on of the solenoids I83 for operating their valvemechanisms is controlled by a switch means, designated in general by2I8. and controlled by a main actuator 2 I9 that acts constantly inresponse to the pressure in th storage receiver 24 and by the actuatingelement I3I. The switch mechanism 2I8 may be arranged in a suitablecasing 220 and supported by a frame 22I attached to a convenient support(not shown) by bolts 222. The switch means comprises a series of circuitmaking and breaking devices including stationary contacts 223. 224, 225and 226 that may be mounted upon a suitable panel and coo erate,respectively, with movable contacts 221. 228, 229 and 230 forcontrolling the flow of electrical ener y to the solenoids. The movablecontacts are pivoted at their upper ends upon a pin 23I and areconnected, by wires 232, to a ground 233.

Intermediate the ends of the movable contacts are rollers 234 forengagement with the peripheral surfaces of cams 235. 236, 231 and 238serving, respectively. to actuate the movable contacts 221,- 228, 229and 230. The. peripheral contour of each cam is described by two radiiof different lengths and consists of semi-cylindrical surfaces 239 and240 of approximately equal length and joined by curved surfaces 24I thatmay substantially conform with the curvature of the rollers 234.

The cams are arranged upon a sleeve 242 and mixed to said sleeve in anysuitablemanner, as for example by set screws 243. The sleeve 242 is, inturn, disposed about a shaft 244 and secured thereto by a set screw 245.The shaft 244 extends through and is journaled in a hollow shaft 246which itself is journaled in the frame 22I. The shaft 244 may beadditionally supported adjacent the outermost cam 235 by a bearing 24Tdepending from the frame 22 I.

The hollow shaft 246 carries a gear 248 that may be suitably affiXed tothe shaft and meshes with the rack I29 of the actuating element I3I. Thehollow shaft also carries at its outer end a gear casing 249 thatcontains an internal ring gear 250 which may be secured to the gearcasing in any well known manner and meshes with a pinion I carried by acover 252 for the gear casing. The pinion 25I also meshes with a gear253 carried by the shaft 244 for transmitting movement from one shaft tothe other.

The gear casing 249 and thecover 252 are ro-,

' tatable with respect to each other,'as will, be

readily understood from the foregoing description, and the cover 252 isrotatable upon the of the main actuator 2I9 is applied for rotating theshaft 244 and such other elements as may rotate in consequence of themovement of the said shaft.

Although any suitable main actuator may be employed to serve thispurpose it is preferred that, as indicated in Figure 9 of the drawings,it consists of a flexible tube 256 bent into the form of a circular arethat is supported intermediate its ends by a bracket 25! to which isconnected a conduit 258 for conveying pressure from the storage receiver24 into the tube 256 to cause the curvature of the portions of said tubelying .on opposite sides of the bracket 25'! to vary in response to thefluctuations ,of the pressurein the storage receiver. The bracket 25'!may, as illustrated, have an extension 259 that terminates near the endsof the tube and carries a cross piece 260 wherein are arranged screws26I that serve as adjustable seats for ends 262 of arms 263 on the endsof the tube 256 and extending transversely thereof.

Each end of the tube 256 may be attached to an intermediate portion ofan arm in any suitable manner, and in the ends 264 of the said armslying outside of the tube are adjustable eye-bolts 265 the eyes of whichare connected to the ends of a tension spring 266 that acts to resistoutward movement of the unsecured portions of the tube 256 with respectto each other.

In the arrangement shown the free end of th extension 259 terminatesbetween the ends of the tube 256 and carries a pivot pin 26'! thatextends through an intermediate portion ofa lever 268 the inner end ofwhich is pivotally connected to an end of a link 269 that is pivotallyattached with its other end to an end of the tube 256. In like manner alink 210 is pivotally connected at one end to the other end of the tube256 and said link 2' I0 is pivotally attached to the lever 268 at apoint intermediate the pivot pin 26'! andv the outer end of the saidlever. The points at which the links 269 and 210 are connected to thelever 268 are located equidistantly from the pivot pin 261 so that whenthe free moving portions of the tube 256 uncurl, or tend to assume theirnormal shapes, the force resulting from such movements tact between therod 21! and the levers and thereby minimize friction between theseelements. I To the end that the levers 255' and 268' will at all timesbe held firmly againstrelative movement a tension spring 213 is attachedto the outer end of the lever 255 and to the corresponding end of thelever 268 to exert a constant; pull upon the said levers for holdingthem firmly against the rod 21 I.

As a preferred arrangement, the energization of the solenoids I83 iscontrolled by suitable relay switches which are themselves controlled bythe switch means 2l8. To thisend the wires 214, 215', 216 and 211leading from the stationary contacts 223, 224, 225 and 226 areconnected, respectively, to relays 218, 219, 280 and 28% and theelectrical current for operating the relays is supplied thereto by awire 282 that is connected to a wire 283 of a primary circuit by meansof a switch 284 that also forms a connection between the other wire 285of the primary circuit and a ground 286.

The relays 218, 219, 280 and 28I may be of any suitable type to operatesuitablespring-pressed linkage 281 for actuating tilt switches 28-8,289;v 290 and 29I, respectively, of the mercury type, that control thecircuits of the solenoids Each tilt switch has the usual pair of wires292 and 293, the former being connected to the core of the solenoids andto a wire 294 leading to a ground 295. The wires 293. on the other hand,are com nected to a wire 296 that may, as showmbe connected to the wire282 and is, therefore, also controlled by the hand switch 284;

In the operation of the compressor, and again assuming that the pressurein the receiver system is between the minimum and maximum values atwhich the load controlling devices become operative, all or the tiltswitches 288 to 29I inelusive will be in position to effect energizationof the solenoids I83. All of the arms 260' of the valve mechanisms I19l82 will then occupy their uppermost limiting positions to open thevalves I92 so that pressure fluid: will flow from the stor age receiver24 through the chambers I81 to the clearance valves for holding all theclearance valves in the closed positions and to cause all the bellows ofthe actuating element I3I to be fully extended.

In these positions of the parts all of the rollers 234 rest upon thesurfaces 239 of their respective cams although at different distancesfrom the adjacent ends of the surfaces 239. Thus; the roller 234 of thecontact 221 may rest closely adjacent the juncture of the surfaces-239and HI of the cam 235 and the rollers of the contacts 228, 229 and 230will lie at progressively increas ing distances from the correspondinpoints of the cams controlling them All of the movable contacts willthen be in engagement with the stationary contacts and the relays 218 to281 will be energized and the tilt switches will be positioned to closethe circuits of the solenoids I83.

Under these conditions the compressor will be operating at full load andif then the discharge output of the compressor exceeds the demand upothe receiver system, so that the pressure within the storage receiverreaches the maximum that it is intended to maintain therein, the tube256 will be caused to uncurl. This action of the tube, transmittedthrough the links 269 and 210, will tilt the outer ends oi the lever 268and 255 upwardly and cause the pinion 25I' to describe a and the'shaft244 and the cams 235 to 238 to rotate in a clockwise direction.

Upon a slight degree of rotative movement of the cams, in the directiondescribed, the roller 234 of the contact 221 will drop from the arc 239to the are 240. The contact 221 will then be out of engagement with thecontact 223 and the circuit oi the relay 218- will be open. Thespringpressed linkage of this relay will then act to tilt the switch 288and open the circuit of the solenoid controlling the valve'mechanismI159. The armature 203 of said solenoid will then descend, to theposition shown in Figure 13, thereby permitting the valve I92 to move toits closed position, for-cutting oli communication between pressurefluid supply and the conduit 2%, and at the same time the arm 2B0 willopen the valve I 98 to communicate the chamber I81 with the dischargeconduit I85.

In the new positions of the valves I92 and I93 pressure fluid willescape from the clearance valves 2129 to the atmosphere andsimultaneously pressure fluid will escape from the bellows I38 and E39of the pair designated hit. The flow of pressure fluid from the saidprimary bellows will take place at the same rate as the exhaust of fluidfrom the clearance valves so that a partial rotative movement, in aclockwise direction as Figure 10 is viewed from the right hand and ofthe drawings, is imparted to the cams to position the roller 234 of thecontact 228 approximately midway between its former position and theendof the surface 239.

7 By reason of the restricted now of flu d from the secondary bellowsI39 01 the pair tilt said secondary bellows will contract comparativelyslowly but in so doing will impart an additional gradual rotativemovement to the cams to bring the cam 233 to aposition in which theroller 23d of the contact 238 rests immediately adjacent the end of thesurface 239. In these pos'tions ol the parts the compressor will beoperating at threequarter load, and if the discharge output of thecompressor thereafter continues to exceed consumption only a slightincrement in the value of the pressure in the receiver system isrequired to effect a slight uncurling movement of the tube 256 foractuating the cams the slight distance required to enable the roller 234of the contact 223 to drop from the surface 239 to the surface 24B ofthe cam 236.

The crcult of the relay 219' will thereby be opened so that the solenoid583 of the valve mechanism I will be deenergized. The valves I92 and I93of said valve mechanism I88 will then be shifted to exhaust the fluidfrom the clearance valves 3I33, for efiecting anotherstep of unloading,and to exhaust pressure fluid from the bellows constituting the pairI35. These bellows will then collapse successively and will act in themanner described in connection with the pair of bellows I34 to againposition the cams in-such v wise that only a slight increase in thevalue of the ously described, it is, however, not necessary that all theload-controlling devicesbpe'rate in the order described untilthecompressor is completely unloaded before additional load may be appliedto the compressor. Thus, if it be assumed that with the compressoroperating at, say, one-half load, the demands upon storage fluid lowerthe pressure value thereof to the predetermined minimum the switch means218 and the load-controlling devices controlled thereby will be causedto actto apply an additional step of loading to the compressor.

This take place as follows: Upon the occurrence of a decrease in thevalue of the storage pressure this pressure drop is reflected in theaction of the tube 256. The unsupported portions of said tube will moveto assume their normal shapes thus tilting the outer end of the lever268 downwardly. Inasmuch as the lever 212 must describe a similarmovement the differential gearing including the pinion 25I and the gear252 will operate to rotate the cams in a counter-clockwise direction, asFigure 10 is viewed from the right hand end of the drawings. Thismovement of the cams will continue during a falling receiver pressureand when such pressure reaches a predetermined minimum value the camswill have reached a position in which the roller 2340f the contact 228will rest adjacent the end of the surface 239. In this way the contact228 is brought into engagement with the stationary contact 224 and therelay 219 is thereby energized.

Upon energization of the relay 219 its linkage 281 will tlt the switch289 for energizing the solenoid I83 of the valve mechanism I80 and causethe armature 203 to tilt the bar 200 upwardly. This movement of the bar200 will unseat the valve I 92 and enable the valve I 98 to be moved toits seat by the spring acting against said valve. In the new positionsof the valves pressure fluid will fiow from the recess I88 through thechamber I81, the conduit 23'! and associated conduits to the clearancevalve 3I33, for closing them, and to the pair of bellows I35.

The compressor will then be three-quarters loaded and the primarybellows I33 of the pair I35 will be immediately extended to its fulllength and thereby impart a partial movement to the cams of the switchmeans so that the roller 234 of the compressor, a plurality of actuatorsfor actuating the said means to a controlling position controlled by thefirst-mentioned means to cause operation of an actuator during eachoper-- ation of the first said means, andmeans responsive to a variationof the pressure'in the receiver occurring subsequently to suchpositioning of the first-mentioned means for further actuating thefirst-mentioned means to efiect the operation 01 anotherload-controlling device.

2. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansfor controlling the operation of the load-controlling devices acting inresponse to variations in the pressure in the receiver to efiect astep-by-step variation in the load of the of the contact 221 will belocated more closely to the end of the surface 240. Meanwhile arestricted flow of pressure fluid into the secondary bellows I39, of thepair I35, i taking place and aid bellows is being gradually extended toslowly rotate the cames to a position in which the roller 234 rests uponthe curved surface 2. These parts are then in such relative positionsthat only a very slight further decrease in the value of the pressure inthe receiver system. as reflected through the action of the tube 256 andelements operated the'reby, will effect a sight rotative movement of thecams sufficient to place the end portion of the surface 239 of the cam235 beneath the'roller 234 carried by the contact 221. The devicesacting in response to th closing of the contact 221 will then operate toapply the final step of loading to the compressor.

I claim:

1. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansfor controlling the operation of the load-controlling devices acting inresponse to variations in the pressure in the receiver to effect astep-by-step variation in the load compressor, a plurality of pressureresponsive actuators for actuating the said means to a controllingposition upon operation of a load controlling device and beingcontrolled by the first mentioned means to cause operation of anactuator during each operation of the first said means. and meansresponsive to a variation in the value of the pressure in the receiveroccurring subsequently to such positioning of the first-mentioned meansand operatively connected to the first-mentioned means for actuating thefirst said means to efiect the operation of another loadcontrollingdevice.

3. The combination of a compressor, a plurality of load-controllingdevices for effecting a stepby-step loading and unloading of thecompressor. a receiver for the discharge output of the compressor, meansfor controlling the operation of the load-controlling devices acting inresponse to variations in the pressure in the receiver to efiect astep-by-step variation in the load of the compressor, a plurality ofactuators each connected tooperate simultaneously with aload-controlling device for effecting additional steps of adjustment ofthe first-mentioned means toward a loadcontrolling position and beingcontrolled by the first-mentioned means, and means acting responsivelyto a variation in the value of the pressure in the receiver occurringsubsequentl to such positioning of the first-mentioned means foractuating the first said means to effect the operation of anotherload-controlling device.

4. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of the compressor, a receiver for the discharge output of the compressor, meansfor controlling the operation of the load-controlling devices, aplurality of groups of actuators acting to impart a plurality of stepsof adjustment to the first-mentioned means for moving saidfirst-mentioned means from one load-controlling position to another andbeing controlled by the said firstmentioned means, and means actingresponsively to a variation in the value of the pressure in the receiveroccurring subsequently to such positioning of the first-mentioned meansfor actuating the first said means to effect the operation of anotherload-controlling device.

5. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansacting in response to the pressure within the receiver for successivelyinitiating action of the load-controlling devices in accordance withvariations in the pressure in the receiver, and means controlled by thefirst said means and operatively connected thereto to effect additionalsteps of adjustment of the firstmentioned means for moving thefirst-mentioned means from one load-controlling position to another.-

6. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansacting in response to the pressure within the receiver for successivelyinitiating action of the load-controlling devices to effect astep-by-step Variation in the load of the compressor, and pressureresponsive actuators operatively connected to the said means to cheatadditional steps of adjustment of the said means to advance said meanstoward a load-controlling position.

7. The combination of a compressor, a plurality of load-controllingdevices for efiecting a stepby-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansacting in response to the pressure within the receiver for successivelyinitiating action of the load-controlling devices to effect astep-by-step variation in the load of the compressor, and a plurality ofgroups of pressure responsive actuators for imparting a series orimpulses to the said means and the actuators of a group actingsuccessively to actuate the said means toward a load-controllingposition.

8. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansacting in response to the pressure within the receiver for successivelyinitiating action of the load-controlling devices to effect astep-by-step variation in the load of the compressor, a plurality ofpressure responsive actuators controlled by the said means to operatesimultaneously with the operation of a loadcontrolling device to movethe said means toward a new load-controlling position.

9. The combination of a compressor, a plurality of load-controllingdevices for efiecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansacting in response to the pressure within the receiver for successivelyinitiating action of the load-controlling devices to effect astep-by-step variation in the load of the compressor, and a plurality ofpairs of pressure responsive actuators controlled by the said means andoperatively connected thereto and the actuators of a pair actingsuccessively to move the said means in step-by-step fashion toward aloadcontrolling position.

10. The combination of a compressor, a plurality of load-controllingdevices for effecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansacting in response to the pressure within the receiver for successivelyinitiating action. of the load-controlling devices to effect astep-by-step variation in the load of the compressor, and a plurality ofpairs of pressure responsive actuators controlled by the'said means, andone pressure responsive actuator of a pair operating simultaneously withthe operation of a load-controlling device and the other actuator ofsuch pair operatin subsequently to the operation of said one pressureresponsive device to move said means toward a load-controlling position.

11. The combination of a compressor, a plurality of load-controllingdevices for eiiecting a step-by-step loading and unloading of thecompressor, a receiver for the discharge output of the compressor, meansmovable to different controlling positions for causing the operation ofthe load-controlling devices to effect a step-bystep variation in theload of the compressor, a plurality of pairs of pressure responsiveactuators acting successively for moving said means from one controllingposition toward another and one actuator of 'a'pair operatingsimultaneously with the operation of aload-controlling device, means forcausing a delayed action of the other actuator of such pair, and meansresponsive to a variation in the value of the pressure in the receiveroccurring subsequently to the action of the second acting actuator foractuating the first-mentioned means to effect the operation of anotherloadcontrolling device.

12. The combination of a compressor, a plurality of pressure fluidactuated load-controlling devices for efiecting a step-by-step loadingand unloading of the compressor, a receiver for the discharge output ofthe compressor meansfor controlling the operation of theload-controlling devices, a plurality of spring-pressed bellows foractuating the said means from one controlling position to another andbeing controlled by the said means to initiate action of said bellowssi-' multaneously with the operation of the load-controlling devices,and means responsive to variation of the pressure in the receiveroccurring subsequently to the operation of the load-controlling devicesand the bellows for actuating the firstrnentioned means through aload-controlling position. c

13. The combination of a compressor, a plurality of pressure fluidactuated load-controlling devices for effecting a step-by-step loadingand unloading of the compressor, a receiver for the discharge output ofthe compressor, means for controlling the admission and exhaust ofpressure fluid to and from the. load-controlling devices, a plurality ofspring-pressed bellows for actuating the said means from oneload-controlling position to another, means to afiord constantcommunication with a bellows and a loadcontrolling device to assure thefiow of pressure to and from a bellows simultaneously with the admissionand exhaust of pressure fluid to and from an associated load-controllingdevice, and means responsive to a variation of 'the pressure in thereceiver occurring subsequently to the operation of a load-controllingdevice and its associated bellows for actuating the first-mentionedmeans through a load-controlling position.

14. The combination of a compressor, a plurality of pressure fluidactuated load-controlling devices for efiecting a step-by-step loadingand unloading of the compressor, a receiver for the discharge output ofth compressor, fluid actuated valves for controlling the flow ofpressure fluid to and from the load-controlling devices, a pilot valvefor controlling the flow of pressure fluid to and from the fluidactuated valves, a plurality of pairs of spring-pressed bellows foractuating the pilot valve from one controlling position to another,means to afiord constant communication between a load-controlling deviceand a pair of bellows, means for causing a delayed action of one bellowsof a pair, and means acting responsively to a variation of the pressurein the receiver occurring subsequently to the operation of aload-controlling device and its associated pair of bellows for actuatingthe pilot valve through a load-controlling position to initiate actionof another load-controlling device and the pair of bellows-associatedwith such other load-controlling device.

15. The combination of a compressor, a pinrality of pressure fluidactuated load-controlling devices for effecting a step-by-step loadingand unloading of the compressor, a receiver for the discharge output ofthe compressor, valve means for controlling the admission and exhaust toand from the load-controlling devices, electro-responsive devices foractuating the valve means, switches for the electro-responsive devices,control means for the switches, means for actuating the control means,to controlling positions with respect to the switches and beingcontrolled by the valve means, and means acting responsively to apredetermined slight variation in the value of the pressure in thereceiver occurring subsequently to such positioning of the control meansto actuate the control means for operating a switchand thereby cause theoperation of an electro-responsive device and a valve means associatedtherewith for efiecting the operation of a load-controlling device.

16. The combination of a compressor, a pinrality of pressure fluidactuated load-controlling exhaust of pressure fluid to and from theloadcontrolling devices, individual electro-responsive devices for eachvalve means, individual switch means for the electro-responsive devices,control means for the switch means, means operating in response to theoperation of the valve means for moving the control means to itscontrolling positions, and means acting respcnsively to a predeterminedvariation in the value of the pressure in the receiver occurringsubsequently to such positioning of the control means to move thecontrol means through a controlling position and thereby cause theoperation of an electroresponsive device and its associated valve meansfor effecting the operation of a load-controlling device.

17. The combination of a compressor, a plurality of pressure fluidactuated load-controlling devices for effecting a step-by-step loadingand unloading of the compressor, a receiver for the discharge output ofthc compressor, individual electricall operated devices for controllingthe operation of the load-controlling devices, individual switches forthe electrically operated devices, control means for the switches, meanscontrolled by the electrically operated devices for moving the controlmeans from one controllin position to another, and means actingresponsively to the variation of pressure in the receiver occurringsubsequently to such positioning of the control means for actuating thecontrol means to effect the operation of a switch and thereby cause theelectrically operated device associated with such switch to initiatetheoperation of a load-controlling device.

PAUL A. YERGER.

